Modeling of the human eye is often necessary for studying optometric systems, such as eyeglasses, contact lenses, and intraocular lenses.  We have performed in-depth studies of contact lenses and corneal-resphaping using novel lens shapes. 

We start with a standard eye model, in this case the Liou & Brennan 1997 model. 

Layout of the Liou & Brennan 1997 eye model

Next we processed data from an actual patient’s corneal topographic measurement and imported this as the first surface of the ZEMAX eye model. 

Surface sag of a measured corneal topographic map

This cornea map was adjusted in position on the front of the eye model until optimal imaging was achieved.  The wavefront map below shows that, in this case, the imaging ability of this patient’s cornea is very poor (more than 1.25 waves of RMS wavefront error).  This correlated well with the fact that this patient’s actual vision was quite poor.

Wavefront map of human eye model with measured cornea map

We added a novel contact lens shape to the front of this model and showed that imaging properties with this new lens not only improved the patient’s far vision, but also drastically improved the patient’s near vision (without any accommodation by the eye’s crystalline lens).  This effect is known as “simultaneous vision” and shows great promise as a cure for presbyopia.

The plots below show simulated images that are formed on the retina of the model, at far and near object distances (infinity and 600mm, respectively).  Because the model does not allow for accommodation by the eye’s crystalline lens, the images below simulate very closely the images that would be seen by this presbyopic patient when using the novel contact lens. Ability to resolve the bottom row in each eye chart represents 20/20 Snellen visual acuity.

Simulated retinal image formed by the novel contact lens when the object is located at infinity

Simulated retinal image formed by the novel contact lens when the object is located at a distance of 600mm

For comparison, below are simulated retinal images formed by the standard Liou & Brennan eye model.  Again, because this model does not allow for near/far accommodation, the images below show what a presbyopic patient with perfect far vision would see.

Simulated retinal image formed by a perfect eye when the object is located at infinity

Simulated retinal image formed by a perfect eye when the object is located at a distance of 600mm

CODE, Inc. completed a final report for this project and it is available for download along with other documents from our e-library.